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The “Focus Point on the Transition to Sustainable Energy Systems” in the European Physical Journal Plus (EPJ Plus) tries to answer central questions regarding the planned Energy Transition, focusing on the power sector in Europe. Important is the role played by intermittent renewables as a low carbon electricity source, central in the plans by the EU Commission in its Energy Roadmap 2050. Their intermittency however strongly reduces efficiency and security of supply and back up by other systems is unavoidable – large storage and/or nuclear and/or fossil based. Storage of excess electricity production by intermittent renewables at the level required seems far-fetched at this moment and much more research will be needed before this can substantially contribute. With a limited contribution of dispatchable renewable electricity (hydro, bio-fuels etc.) and excluding à priori nuclear power, on various grounds, a continued use of fossil fuels imposes itself to guarantee a secured supply of electricity – in strong contrast with the original aims of the EU Energy Roadmap 2050. A rational debate involving all options is urgently needed and it is hoped that the set of papers in this focus point can contribute to improve insights in a determining factor for the future of our children and grandchildren.

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3D simulations reveals that every part of the human heart works in combination with the others, while all parts influence each other’s dynamics, giving clues to help prevent cardiac conditions

Did you know that the left side of the heart is the most vulnerable to cardiac problems? Particularly the left ventricle, which has to withstand intense pressure differences, is under the greatest strain. As a result, people often suffer from valve failure or impairment of the myocardium. This is why it is important to fully understand how the blood flow within this part of the heart affects its workings. In a new study published in EPJ E, Valentina Meschini from the Gran Sasso Science Institute, L'Aquila, Italy and colleagues introduce a novel model that examines, for the first time with this approach, the mutual interaction of the blood flow with the individual components of the heart. Their work stands out by offering a more holistic and accurate picture of the dynamics of blow flow in the left ventricle. The authors also perform some experimental validations of their model.

The personal memories of Jayant Narlikar point to the need for restoring cosmology as the flagship of astronomy

"Cosmologists are often wrong but never in doubt”, Russian physicist Lev Landau once said . In the early days, astronomers began by observing and modelling stars in different stages of evolution and comparing their findings with theoretical predictions. Stellar modelling uses well-tested physics, with concepts such as hydrostatic equilibrium, law of gravitation, thermodynamics, nuclear reactions etc. Yet in contrast, cosmology is based on a large number of untested physical assumptions, like nonbaryonic dark matter and dark energy whose physics has no proven link with the rest of physics. In a recent paper published in EPJ H, Jayant V. Narlikar, professor emeritus at the Inter-University Centre for Astronomy and Astrophysics in Pune, India, shares his personal reminiscences of the evolution of the subject of cosmology over six decades. He tells of the increase in our confidence in the standard model of cosmology to the extent that it has become a dogma.

Snapshots of contact line configurations when water droplets slide on surfaces with micro-pillars.

New theoretical model explains experimental measurement of the friction of liquid droplets sliding on micro-structured surfaces

The wetting and adhesion characteristics of solid surfaces critically depend on their fine structures. However, until now, our understanding of exactly how the sliding behaviour of liquid droplets depends on surface microstructures has been limited. Now, physicists Shasha Qiao, Qunyang Li and Xi-Qiao Feng from Tsinghua University in Beijing, China have conducted experimental and theoretical studies on the friction of liquid droplets on micro-structured surfaces. In a paper published in EPJ E, the authors found that under the same solid fraction, friction on surfaces with a structure made up of micro-holes is much higher than that on surfaces patterned with an array of pillars. Such micro-structured surfaces have helped design new surfaces that mimic surfaces found in nature, such as self-cleaning surfaces, reduced-drag surfaces, surfaces capable of transporting liquids in microfluidic systems, variants with anti-icing or heat transfer properties, and even surfaces that facilitate oil-water separation.

Cloning of quantum states is used for eavesdropping in quantum cryptography. It also has applications in quantum computation based on quantum information distribution. Uncertainty at the quantum scale makes exact cloning of quantum states impossible. Yet, they may be copied in an approximate way - with a certain level of probability - using a method called probabilistic quantum cloning, or PQC. In a new study published in EPJ D, Pinshu Rui from Anhui Xinhua and Anhui Universities, based in Hefei, China, and colleagues demonstrate that partial PQC of a given quantum state secretly chosen from a certain set of states, which can be expressed as the superposition of the other states, is possible.

Although urbanization has many advantages, one of its biggest drawbacks is the rise in socio-economic inequality. There have been some attempts at a qualitative analysis of the relationship between certain city features and social inequality, but these kinds of analyses are hard to replicate. A new research article published in EPJ Data Science proposes a new quantitative computer-based method for how to better understand the link between cites and social inequalities.

The most precise ever laser satellite measurement method provides new clues to relativity

Tides on Earth have a far-reaching influence, including disturbing satellites’ measurements by affecting their motion. This disturbance can be studied using a model for the gravitational potential of the Earth, taking into account the fact that Earth’s shape is not spherical. The LAser RElativity Satellite (LARES), is the best ever relevant test particle to move in the Earth’s gravitational field. In a new study published in EPJ Plus, LARES proves its efficiency for high-precision probing of General Relativity and fundamental physics. By studying the Earth’s tidal perturbations acting on the LARES, Vahe Gurzadyan from the Center for Cosmology and Astrophysics at Yerevan State University, Armenia, and colleagues demonstrate the value of laser-range satellites for high-precision measurements.

The papers published in this Focus Point evidence the broad range of interests pursued by the Italian community active in the field of Planetary Sciences.

Although this selection of papers can by no means be considered to exhaustively represent the fields of interest of the community, many points of interests and activities are included, from PI activitities in Planetary Space Missions, both from ESA and NASA programmes (such as Bepi Colombo and Juno) to the study of physical and dynamical properties of minor bodies to the geological study of planetary surfaces to the study of atmospheres to cosmogeophysical studies of meteorites.

The Italian Research Institutes, Observatories and Universities hosting research groups active in Planetary Sciences are based in different regional locations on the Italian territory as also shown by the selection of articles published in this Focus Point, and are evidence of a growing interest of the Astrophysical Community in Planetary Sciences and of a rapid growth in the number of topics investigated and in the number of scientists involved.

How magnetic force acts on charged subatomic particles near the speed of light

Current textbooks often refer to the Lorentz-Maxwell force governed by the electric charge. But they rarely refer to the extension of that theory required to explain the magnetic force on a point particle. For elementary particles, such as muons or neutrinos, the magnetic force applied to such charges is unique and immutable. However, unlike the electric charge, the magnetic force strength is not quantised. For the magnetic force to act on them, the magnetic field has to be inhomogeneous. Hence this force is more difficult to understand in the context of particles whose speed is near the speed of light. Moreover, our understanding of how a point-particle carrying a charge moves in presence of an inhomogenous magnetic field relied until now on two theories that were believed to differ. The first stems from William Gilbert's study of elementary magnetism in 16th century, while the second relies on André-Marie Ampère electric currents. In a new study just published in EPJ C, the authors Johann Rafelski and colleagues from the University of Arizona, USA, succeeded in resolving this ambiguity between Ameperian and Gilbertian forms of magnetic force. Their solution makes it possible to characterise the interaction of particles whose speed is close to the speed of light in the presence of inhomogeneous electromagnetic fields.

Understanding the dynamics of message transmission in networks leads to identification of key individuals spreading news and viruses in epidemics

Social networks, such as Twitter, thrive on key influencers spreading news. Like information, epidemics also spread from key individuals. To identify the most influential actors in such networks, many studies have, until now, focused on ranking the influence of individual nodes. But these methods are not accurate enough to single out influential spreaders because they fail to take into account the spreading dynamics. Now, Byungjoon Min from the Institute of Interdisciplinary Physics and Complex Systems, Balearic Island University, Palma de Mallorca, Spain, has calculated for the first time the expected size of epidemic outbreaks when spreading originates from a single seed. In a study published in EPJ B, Min accurately predicts the influence of spreaders in such networks. Applications include viral marketing, efficient immunisation strategies, and identifying the most influential actors in our society.